Gauges for displaying measured values are utilized in a variety of environments such as land vehicles, airplanes, and also watercrafts. Such gauges are commonly used to display fuel level, oil pressure, temperature, etc. In many of the environments, atmospheric conditions exist which may cause the production of fog on the lens of the gauge, especially when the lens becomes cooler than the interior of the gauge and moisture within the gauge deposits on the lens. This fogging is undesirable as it hampers viewing of the gauge display.
U.S. Pat. No. 4,628,731 issued Dec. 16, 1986 in the name Copeland discloses a fog resistant gauge which utilizes two spaced lenses with a surrounding baffle. The baffle "restricts" air flow into and out of the space between the lenses, although some air is allowed to pass therebetween. Both of the lenses are coated with a clear, anti-fog coating. The gauge includes an outer housing or casing which is secured to the baffle adjacent the lenses. Within the outer casing is included an inner casing which includes a vent slot therethrough so that the interior of the inner casing is in communication with the interior of the outer casing so that heat dissipated by the inner casing is in air exchange through the vent. Problems with this type of design is that fogging still exists and the anti-fog coatings disintegrate over time. Furthermore, the lenses are plastic which eventually can pass water therethrough.
None of the prior art gauges have been tested and found suitable for anti-fog and waterproof capability, nor have any satisfied cost and manufacturing considerations.